1. Field of the Invention
The present invention relates to a pneumatic brake booster with a booster housing, which comprises a first and a second housing shell and is subdivided into a working chamber and a vacuum chamber by an axially movable wall to which a pneumatic differential pressure can be applied, with the movable wall being formed of a diaphragm plate and a diaphragm abutting thereon that includes a radially inward sealing bead and a radially outward sealing bead for sealing the two chambers, and the radially outward sealing bead is compressible between the housing shells.
2. Description of the Related Art
DE 41 24 683 A1 discloses a pneumatic brake booster of this type. The radially outward sealing bead of the prior-art brake booster is compressed between two substantially radially configured flanges of the housing shells, and an axially arranged flange is formed at the radial flange of the second housing shell and projects over the radial flange of the first housing shell after the two housing shells have been joined. The operative connection of the housing shells is carried out e.g. by connecting the axial flange by way of lanced indentations in an area surmounting the radial flange of the first housing shell. As this occurs, the radially outward sealing bead is deformed during the joining process of the housing shells in such a fashion that excess volume of the sealing bead is displaced from a mounting space between the flanges into the interior of the brake booster.
Tests have shown that the displacement of the excess sealing bead volume will deteriorate the assembly of the diaphragm, and sealing of the two chambers by the diaphragm is no longer ensured. This leakage inevitably causes failure of the brake booster. The compression of the diaphragm between the housing shells in prior art brake boosters is therefore considered worthy of being improved.